1. Field of the Invention
The invention relates to polyol blends to be used in low density packaging foams and more particularly relates to such blends and foams which use an aromatic polyester polyol made from recycled polyethylene terephthalate and alkylene glycol and dibasic acid waste streams.
2. Description of Relevant Compounds and Methods in the Field
Open-celled, low density packaging foams are widely used for the encapsulation or packaging of shock-sensitive objects. These foams are generally made by mixing two preformulated components, commonly called the A-component and the B-component. The A-component typically contains the isocyanate compound that must be reacted with the constituents of the B-component to form the packaging foam. The B-component contains the balance of the foam ingredients; namely, polyol, water, surfactant, fluorocarbon and amine catalyst. A typical B-component will contain 10 to 30 parts by weight (pbw) water, 15 to 40 pbw fluorocarbon and 100 pbw polyol, plus small quantities of catalyst and surfactant.
U.S. Pat. No. 4,087,389 to Olin Corporation describes packaging foam compositions prepared from a reaction mixture characterized by high levels of water and an organic foaming agent, and a reaction mixture NCO/OH index of from about 30 to about 60. The composition employs a triol obtained by condensing one mole of glycerine first with propylene oxide, then with ethylene oxide. Canadian Pat. No. 866,233 is another patent in this field that discloses how low density, open-celled polyurea foams may be made by reacting undistilled aromatic polyisocyanurates with water.
Another type of polyisocyanurate foam employs a polyol blend using both amide diols and primary hydroxyl polyols to give a foam having a large reaction exotherm, making it particularly suited to the preparation of polyisocyanurate foam laminates, according to U.S. Pat. No. 4,246,364.
As noted, one of the polyols used in the invention herein is an aromatic polyester polyol made from scrap polyethylene terephthalate (PET). Scrap PET is known to be incorporated into polyurethanes. For example, U.S. Pat. No. 4,048,104 relates that polyisocyanate prepolymers for use in polyurethane products may be prepared by combining an organic polyisocyanate with polyols which are the hydroxylterminated digestion products of waste polyalkylene terephthalate polymers and organic polyols. A polyol ingredient which is the digestion product of polyalkylene terephthalate residues or scraps digested with organic polyols is also described in U.S. Pat. No. 4,223,068. Another case where terephthalic acid residues are employed is outlined in U.S. Pat. No. 4,246,365 where polyurethanes are made from polyesters containing at least two hydroxyl groups and terephthalic acid residues.
Also relevant to this plyol portion of the invention is U.S. Pat. No. 4,237,238. In this patent, a polyol mixture is prepared by the transesterification of a residue from the manufacture of dimethyl terephthalate with a glycol, which is then used to produce polyisocyanurate foams having a combination of a high degree of fire resistance with low smoke evolution, low foam friability and high compressive strength. The preparation of such a polyol mixture (from ethylene glycol and dimethyl terephthalate esterified oxidate residue) is described in U.S. Pat. No. 3,647,759. J. M. Hughes and John Clinton, in the Proceedings of the SPI 25th Annual Urethane Division Technical Conference, Scottsdale, Arizona (October, 1979), describe other foams prepared from the polyols of U.S. Pat. No. 3,647,759. However, one of the problems with the polyols of U.S. Pat. No. 3,647,759 is that they are not very compatible with trichlorofluoromethane, the gas commonly used as a blowing agent.
Another of the polyols used in the invention herein is made as described in U.S. Pat. No. 4,137,265, incorporated by reference herein.